Many engineering vehicles, such as excavators, backhoes, and cranes, include an elevated cab. These elevated cabs are frequently positioned at a significant distance from ground level. Due to the difficulty of climbing into or out of elevated cabs, falling from engineering vehicles in the process of cab entry or exit is a common cause of injury to equipment operators.
Cab assemblies have been designed which allow a vehicle cab to be moved into different positions. Some of these cab assemblies, while enabling the cab to be moved from one operating position to another, are not designed to lower the cab to a position at or near ground level. For example, U.S. Pat. No. 4,427,090 describes a cab assembly which moves a cab between two supporting plates that are each mounted on a vehicle chassis. U.S. Pat. No. 5,890,557 describes a cab assembly which enables a cab to be lowered to rest on a pedestal on the chassis of a tractor. Neither of those cab assemblies allows a cab to articulate to a ground level access position.
An example of a cab assembly that enables a cab to be lowered to a ground level position is depicted in U.S. Pat. No. 3,891,264. The cab assembly is mounted to the side of the vehicle. The cab is lifted by the retraction of hydraulic cylinders, which causes rocker arms to pivot rearwardly, thereby lifting the cab. The cab may be moved upwardly and downwardly along the side of the vehicle body, and may pivot around a corner of the vehicle body. The cab may not be lifted to a position in which the cab, or a portion of the cab, is lifted directly above the elevated frame of the vehicle.
Another example of a movable cab assembly is depicted in U.S. Pat. No. 7,419,023. This cab assembly utilizes a telescopic boom to lower the cab from an elevated position. A cab support extends underneath the cab, limiting how close to the ground the cab itself may be positioned.
A need exists for a cab assembly which is able to lower a cab safely to ground level, while also enabling the cab to be moved between a range of operating positions that may improve the operator's vantage point.